Menu items are left orphaned when a linked entity is removed

[jonasraoni]

Describe the bug
This issue is an extension of #10511.

When removing an entity that's linked to a menu item, the menu item is left orphaned.

Note: Such orphan menu item is currently hidden, together with its children menu items.

Related issue: #10095

Possible solutions (sorted by my personal preference):
A. Clear the relationship and turn such items into a placeholder (e.g. a menu which just holds text).
B. Remove the menu item. If it's a parent, its children can be brought one level up.
C. Clear the relationship and keep the current behavior (hide the menu and its children)
D. Delete the menu and its children.
E. Block the removal of the related entity until there's nothing linking to it.

To Reproduce

1. Create a menu item which is linked to an entity (e.g. category).
2. Remove the referenced entity.
3. See the menu is kept.

What application are you using?
3.3